Is he dreading what Blair's thinking?

Election: The deal - If Labour wins another landslide, as now seems possible, will the Prime Ministe

There has been no deal between Tony Blair and Gordon Brown. There has been no promise on the succession, verbal or written. On this point both sides are adamant. So where does this leave voters, and the large contingent of disgruntled Labour supporters who might be persuaded by the Chancellor to keep the faith?

When Alastair Campbell went to see Brown in Scotland over the Easter holidays to persuade him to appear in an election broadcast, Brown agreed to discuss it further with Blair. The truce that followed was based on an understanding about the way the campaign would be conducted. Life after polling day was not discussed. Brown did not want to be seen to be making his co-operation conditional. In any case, he doubted, in the light of past experience, whether any deal would be watertight.

Brown did achieve the following: he ensured that plans to move him to the Foreign Office were quashed; he ensured that the economy would be the centrepiece for the campaign; and he ensured that his two right-hand men, the future MPs Ed Balls and Ed Miliband, join the election strategy committee. These conditions were explicit. Anything else was implicit.

By the time Brown belatedly became involved in the manifesto, he and his people were pleasantly surprised at its tone and contents. They saw his mantra of the progressive consensus had already been included. They saw that nothing had been slipped in, unlike the 2001 manifesto, with its heavy focus on private provision in the NHS. The timing and detail of the next phase of public service reform remains to be agreed, but Brown had no substantive objections to the manifesto contents. He requested more of an emphasis on tax credits, particularly child tax credits, and that was agreed. In the manifesto launch, and in the various press conferences since, Blair has focused far less on choice and diversity of provision and much more on defining Labour's management of health and education against the Conservatives - territory on which Brown was entirely comfortable. The triangulation of old has been ditched, for the moment at least. The more they have rediscovered the art of working together, the more Blair, Brown and their respective entourages have felt at ease. I am told that Brown and Alan Milburn are even able to converse, something that would have been unthinkable even a few weeks earlier.

This is less about peace than, in the words of one senior party official, a coincidence of interests. The Blair camp has for some time been divided into two groups: those who have sought consensus with Brown, led by Campbell, Philip Gould and John Prescott; and those who have wanted to marginalise him. Blair fluctuated between the two, but was finally persuaded by Gould's private polling on the gulf between the PM's personal trust ratings and those of Brown that he needed his Chancellor after all. Brown has delivered on his side of the bargain. "Gordon has neutralised much of the anti-war hostility," says one cabinet minister not usually generous to him. Note that the Chancellor has avoided all attempts during the campaign to pin him down on Blair's handling of Iraq. But by standing so close to Blair on all other issues, he is sending a subliminal message to disgruntled voters that it is safe for them to return to the fold.

The rewards for his efforts, however, are still indeterminate. Brown had nothing to gain, in the long term, from a diminished Labour majority. He needs as much of a buffer as he can get to withstand a combination of factors working against him in 2009/2010: the possibility that the Conservatives might, finally, learn from defeat and present a more palatable alternative next time around; boundary changes that will reverse much of the current pro-Labour bias; and a general sense of the inevitability of a cyclical political shift that, as John Major found in the mid-Nineties, a new leader struggles to withstand.

The logic of the campaign suggests that the balance of forces is moving inexorably towards the successor. It confirms Blair's dependency on Brown and the defeat of forces that seek to deny the Chancellor the inheritance. But that is not enough of an assurance. The cut-off point - the planned May-June 2006 British referendum on the EU constitution - may now dissolve thanks to the French. So what if Blair decides to stick it out, perhaps for three more years or even more?

Labour is now looking forward to a third successive landslide, or so it seems. The Conservative campaign has run out of steam. The polls should be treated with caution, but Labour's pollsters at key marginals are reporting that the vote is holding up well. Ministers were, for the first months of 2005, contemplating what the disembowelling of Labour's majority would do to the longevity of Tony Blair. Now they are beginning to consider the other scenario. Would another majority of 100-plus persuade the Prime Minister to go on and on? What if Blair convinces himself that it was he who delivered the victory? He would argue that a third landslide had seen off Iraq as an issue, and that he might remain an asset after all. Already some around the PM are talking of Brown's "huge but not necessarily decisive hand" in the result.

The Brownites are working from the same assumptions they made in 2004: that the momentum is moving their way, and that Blair will be forced to be true to his word. The most telling signal is the rapprochement with several cabinet members who had previously been wary or hostile. Those who might have mounted a credible challenge to Brown have fallen by the wayside. The negotiations on the composition of the next cabinet and on the handover will begin on 5 May as voters go to the polls. The timing of the transfer of power could be any point from the next party conference to . . . and there's the rub. Brown, this time, sought no assurance from Blair and has received none. Blair continues to tell his allies he will go on his terms. He has reiterated publicly that his election mandate is to serve a full five years, as he is obliged to say. But what if? As the Prime Minister visibly relaxed in his appearances in recent days, was he genuinely demob happy, or was he thinking what his rival was dreading thinking?